Processing of detecting an object, such as a person or a car, from an image captured by a camera is an important technology applied to a vision sensor for robot or vehicle, an image monitoring system, or the like.
In detecting a desired object, discrimination processing, such as pattern recognition processing based on machine learning, is often used.
Specifically, a window that indicates a local area having an appropriate size is cut out from frames of images continuously captured by a camera, discrimination processing, such as pattern recognition processing, for the image in the window is executed, and it is determined whether an object exists within the window. By these processing, an area in the image in which the object to be detected exists is detected.
It is known that the discrimination processing, such as the pattern recognition processing, has a large amount of operation. In general, a position where an object exists in each frame of an image and a size of the object are unknown. Therefore, the discrimination processing, such as the pattern recognition processing, is continuously executed while slightly changing the size and the position of the window.
For the reason above, an enormous number of times of discrimination processing is needed per frame, resulting in an enormous operation amount.
In Patent Literature 1 below, in order to decrease the number of times of discrimination processing to reduce the operation amount, an object detection device is disclosed, which detects in advance pixels indicating large luminance change in a time direction as an object area and exclusively uses the detected object area as a target for the discrimination processing.